SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a43bb78ca487255990e36ef1cb2efb7f8777c079a7cfcd56e71a756b0c599844' 
  AND token = '0rRCEJBmMd+brVrIqlpKprP+LAmJCscoLFg8/JVXzFA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}